U.S. application 2007/0016185 to Tullis et al, now issued as U.S. Pat. No. 7,918,852, is for an electrosurgical system. It discloses an electrode assembly for lesioning that includes an electrode surrounded by layers of insulation and tubing but does not disclose cooling of the lesioning electrode.
Desinger et al (U.S. application 2004/0167517), now issued as U.S. Pat. No. 7,828,799, discloses a probe having two distal region electrodes with the distal electrode tip having a cone shape that extends distally. Fluid in the lumen of the probe is spaced apart from the furthest point of the distal tip electrode.
Fay et al (pending U.S. application 2009/0156981) discloses a flexible catheter having a plastic tip and a plastic shaft tube with electrodes attached to it.
Some prior art bi-polar probes, such as those described in U.S. application 2004/0167517 to Desinger et al and in U.S. application 2009/0156981 to Fay et al, have configurations that allow cooling fluid to contact both the active electrode and the return electrode. As cooling fluid often has some conductivity, the flow of coolant between the electrodes will cause some energy to be transmitted within the probe rather than to surrounding tissue, resulting in a loss of effectiveness and possible safety concerns. The stray energy can also affect impedance measurements, causing further problems for devices that measure impedance.